1. Field of the Invention
The present invention relates to an application device for a disk brake with:                an application shaft transverse to the application axis;        a first support for supporting the application shaft on an application element, which can move in the direction of the application axis; and        a second support for supporting the application shaft on an abutment,        wherein the first and the second supports have arc-shaped support surfaces on the application shaft, these surfaces curving in the same direction but having imaginary centers which do not coincide; and        wherein the first and/or the second support has a support element which can shift transversely to the application axis.        
2. Description of the Related Art
Brake application devices of the type described above are known from, for example, DE 44 30 258 C1. This application device is a so-called linear applicator, which is designed so that the application element is displaced in linear fashion as soon as the application shaft starts to move. According to DE 44 30 58 C1, this element is a thrust element, which presses the brake lining against the brake disk of the disk brake. Linear application of this type offers considerable advantages over the pendulum type of application.
Additional linear application devices are known from DE 26 14 321 C2, EP 614 024 B1, and EP 589 206 B1.
The application device according to DE 44 30 258 also includes the above-mentioned thrust element, which is inside the caliper, parallel to the plane of the disk brake, and which has at least one extendable thrust spindle. Inside the caliper, the thrust element is supported and guided on at least one slide face parallel to the brake axis in such a way that it can carry the application shaft by way of an appropriate bearing; this bearing defines the center of rotation of the application shaft. On the side facing away from the brake disk, furthermore, the application shaft is supported by a freely rotating roller on the end of the caliper. The application device is tensioned against the rear surface of the caliper by at least one compression spring, as a result of which all the parts rest against each other. The application shaft is thus carried by the thrust element.
So that the displacement will be linear, all of the application devices cited above have either a special brake support system or a brake shaft with a special contour, which functions as a cam. Common to all of them is that a support element is supported by linear contact. Depending on how the brake shaft is supported, this linear contact can be either on the rear surface of the caliper (when the pivot bearing is on the application element) or on the application element (when the pivot bearing is on the caliper).
When the actuation unit provided for these application devices turns the application shaft (by means of an appropriate turning lever), the application shaft causes an increase in the amount of travel, and the thrust element is thus pressed by a pressure spindle, at least one of which is provided, against the brake lining. As a result of the special way in which the application shaft, which is equipped with actuating cams, is supported, and as a result of the special design of the cams and of the roller on the caliper, almost perfect linear movement toward the brake disk is ensured.
The principle described above has been found to be generally reliable for the practical operation of brakes, because it avoids the disadvantageous pendulum-like movements of the differently designed eccentric application devices, in which the application shafts, which carry the thrust elements, rotate around a stationary center in the caliper.
The linear application devices described above, however, are limited with respect to the amount of application forces they can transmit, because it is necessary to avoid overloads in the linear contact area. A conceivable solution would be to increase the diameter or the length of the roller body, so that the load in the linear contact area between the roller body and the rolling surface on the end of the caliper will not exceed a certain allowable limit; as a result, however, more space would be required to house the brake, which would lead to considerable disadvantages. In addition, the linear application devices described above impose high technical requirements on the materials which are used for the contact surfaces. That is, various hardening and grinding processes are always required. In addition, the materials which must be used are very expensive.